IPv6 vs. IPv4: What Is the Difference, and Does Your Business Need IPv6?

Every device on the internet needs an address, and the internet has been running two addressing systems side by side for more than a decade. IPv4, the original, ran out of new addresses years ago. IPv6, its replacement, now carries about half of all internet traffic and nearly all mobile traffic. Most businesses use both every day without knowing it. This article explains the difference, how IPv6 addresses work, the three types of IPv6 address, where adoption stands in 2026, and what a small business actually needs to do about it, which is less than you might fear and more than nothing.

The short version

Why IPv4 ran out

IPv4 addresses are 32 bits long, which allows about 4.3 billion combinations, a number that looked infinite in 1981 and ran out once every phone, camera and thermostat wanted one. The central registry handed out its last blocks in 2011, the North American registry ran dry in 2015 and the European one in 2019. The internet coped by sharing: the address translation in every office firewall lets a whole building hide behind one public address, which is why your internal network uses 192.168 or 10.x addresses that are not unique in the world. Sharing works, but it complicates anything that needs to reach a device directly, and it made public IPv4 addresses a commodity. They are now bought and sold, and cloud providers charge for each one; since 2024, for example, Amazon Web Services bills for every public IPv4 address in use.

How IPv6 addresses work

IPv6 addresses are 128 bits, written as eight groups of hexadecimal digits separated by colons, with runs of zeros collapsed to a double colon: 2001:db8:85a3::8a2e:370:7334. The first half generally identifies the network and the second half the device, and a network is normally given a block large enough that every device can have a public address of its own, configured automatically. There is no address translation, so the firewall, rather than the scarcity of addresses, is what keeps the office private. Devices commonly hold several IPv6 addresses at once, one for the local link, one or more global ones, and temporary ones that rotate for privacy.

The three types of IPv6 address

• Unicast identifies a single device. It comes in three scopes: global unicast, reachable from the internet, generally starting with 2 or 3; link-local, starting fe80, valid only on the local network segment and present on every IPv6 interface; and unique local, starting fc or fd, the IPv6 equivalent of private addresses for use inside an organisation.
• Multicast, starting ff, addresses a group of devices that all receive the same message. IPv6 has no broadcast; multicast replaces it for jobs such as finding neighbours and routers.
• Anycast uses an ordinary unicast address assigned to several devices; a message goes to the nearest one. Large DNS and content networks use it so that you reach the closest server automatically.

Older articles, including the first version of this one, also list IPv4-mapped IPv6 addresses, which embed an IPv4 address inside an IPv6 one for transition purposes. They still exist but are a detail of software rather than a fourth type.

Where adoption stands

Google’s public statistics show close to half of its users reaching it over IPv6, up from about one percent when this article was first written in 2013, and the share is higher in the United States. The big mobile carriers run IPv6-first networks, the large cloud and content providers are dual stack, and the US federal government has been moving its systems to IPv6-only under a 2020 mandate. What has not happened is any decline in IPv4: the two run side by side, called dual stack, and will for a long time. Nobody is going to switch off IPv4, and nobody needs to.

What a small business actually needs to do

1. Do not disable IPv6 on Windows. It is on by default, Microsoft does not support turning it off, and doing so causes slow logins and odd failures. The right response to IPv6 is to handle it, not to hide it.
2. Make sure the firewall filters IPv6. If your internet provider delivers IPv6, and most now do, a firewall configured only with IPv4 rules can pass IPv6 traffic unexamined, straight to devices that have public IPv6 addresses. Every rule you have for IPv4 needs an IPv6 equivalent, or IPv6 should be blocked at the edge until it does. This is the one real security risk, and it is the first thing we check on a new client’s firewall.
3. Leave the internal network on private IPv4. There is no reason to renumber an office; 192.168 addresses behind a firewall will work for years, with IPv6 alongside where devices use it.
4. Check that your website works over IPv6. Most hosts and content delivery networks provide it; an AAAA record in your DNS and any online IPv6 test confirms it. Email is still mostly delivered over IPv4 and that is fine.
5. Ask about IPv6 when buying network equipment and choosing an internet plan; anything current supports it, and anything that does not is a sign of age.
6. Expect to pay for public IPv4 addresses in the cloud and from carriers, and to use IPv6 where a public address is needed and IPv4 is charged for.

The terms in this article, and most others you will meet on a network quote, are in our IT glossary. If your network was set up before IPv6 was common, our network support team will check the firewall rules and DNS for you as part of a review, and why is my network slow covers the other things we look at.

Common questions

Do we need to switch our office network to IPv6?

No. Inside the office, private IPv4 addresses with a firewall doing address translation work fine and will for years. What matters is that IPv6 is handled correctly where it already exists: your internet provider probably delivers it, Windows prefers it, and your firewall must filter it.

Should we disable IPv6 on Windows?

No. Microsoft does not support disabling it, several Windows features depend on it, and turning it off can cause slow logins and strange failures. Leave it on and make sure the firewall treats IPv6 the same way it treats IPv4.

Is IPv6 more secure than IPv4?

Not in itself. IPv6 was designed with IPsec in mind, but it is optional in both versions, and the practical security of a network depends on the firewall, not the address family. The risk with IPv6 is a firewall configured only for IPv4 that lets IPv6 traffic pass unexamined.

What are the three types of IPv6 address?

Unicast, for one device; multicast, for a group of devices that all receive the same message; and anycast, for a group where the nearest device answers. IPv6 has no broadcast address; multicast does that job. Within unicast there are global addresses, link-local addresses starting fe80, and unique local addresses for private networks.

Will IPv4 go away?

Not for a long time. The two run side by side on most networks, called dual stack, and IPv4 is likely to persist for decades. What has changed is cost: IPv4 addresses are scarce and now bought, sold and rented, and cloud providers charge for each public IPv4 address you use.

Does our website need to work over IPv6?

It should, and with most web hosts and content delivery networks it already does. Check with an online IPv6 test or look for an AAAA record in your domain’s DNS. Email is usually still delivered over IPv4, and that is fine.

Talk to us

If you are not sure whether your firewall handles IPv6 or whether your website is reachable over it, we will check both and tell you what, if anything, needs to change. Call 952-548-5558 or contact us; the first conversation is free and there is no long-term contract.